This proposal extends work investigating the role of the plasma membrane in the control of motility and metabolism in human spermatozoa. The role of adenylate cyclase in the control of membrane ion transport and the role of microfilaments in membrane structure and function are explored in intact cells and in purified membrane preparations. Membrane active drugs and their antagonists are used to control motility in intact cells. Fluorescent membrane probes and radioactive isotopes are used to monitor concomitant changes in ion binding to the membrane and ion transport across the membrane. Radioactive cytochalasins are used to isolate and characterize new structural features of the plasma membrane. Structure-Activity relationships and spermicidal activity of membrane-active organoboron compounds will be studied with a view toward their potential as contraceptives.